1. Field
The disclosed concept relates generally to electrical switching apparatus and, more particularly, to electrical switching apparatus, such as circuit breakers. The disclosed concept also relates to secondary trip mechanisms.
2. Background Information
Electrical switching apparatus, such as circuit breakers, provide protection for electrical systems from electrical fault conditions such as, for example, current overloads, short circuits, abnormal voltage and other fault conditions. Typically, circuit breakers include an operating mechanism, which opens electrical contact assemblies to interrupt the flow of current through the conductors of an electrical system in response to such fault conditions as detected, for example, by a trip unit. The electrical contact assemblies include stationary electrical contacts and corresponding movable electrical contacts that are separable from the stationary electrical contacts.
Among other components, the operating mechanisms of some low and medium voltage circuit breakers, for example, typically include a poleshaft, a trip actuator assembly, a closing assembly and an opening assembly. The trip actuator assembly responds to the trip unit and actuates the operating mechanism. The closing assembly and the opening assembly may have some common elements, which are structured to move the movable electrical contacts between a first, open position, wherein the movable and stationary electrical contacts are separated, and a second, closed position, wherein the movable and stationary electrical contacts are electrically connected. Specifically, the movable electrical contacts are coupled to the poleshaft. Elements of both the closing assembly and the opening assembly, which are also pivotably coupled to the poleshaft, pivot the poleshaft in order to effectuate the closing and opening of the electrical contacts.
It is important to that sufficient tripping force is provided to ensure the circuit breaker does, in fact, trip in response to a trip condition.
There is, therefore, room for improvement in electrical switching apparatus, such as circuit breakers, and in secondary trip mechanisms therefor.